Removing enamel from enameled metal articles.



any other purpose to which it may ED STAS ATE RAYMOND D. COOKE, OF TERREHAUTE,

ING & STAMPING'COMPANY, OF TER INDIANA, ASSIGNOR TO COLUMBIAN ENAMEL- REHAUTE. INDIANA, A CORPORATION OF REMOVING ENAMEL FROM ENAMELED METALARTICLES.

To all whom it may concern:

Be it known that I, RAYMOXD D. Coolie. a citizen of the United States,and a resident of Terre Haute, in the county of Vigo and State ofIndiana, have invented a new and useful Improvement in the Art ofRemoving Enamel from Enameled Metal Arti cles, of which the following isa specification.

In the practice of the art of enameling metals there is always a certainamount of loss due to mechanical injury to the enamel or to other causeswhich render an article unfit for profitable disposal on the market. Itis. therefore, highly desirable that a process be found which willremove vitreous enamel cheaply and without undue action on the metal,leaving the metal article in a condition for subsequent enameling or'forbe desired to put it.

My invention consists essentially in treating the article first with anacid solution which causes the enamel to become porous. and which isfollowed by a short. immersion in an alkaline bath which loosens andsoftens the enamel to such an extent that it falls off or may be brushedoff.

In the preferred process I use an acid bath of 10% hydrochloric acidmaintained at a temperature of about, 160 F. by any suitable means, inwhich the enameled article is allowed to remain about fifteen minutes.After removing from this bath the article is washed in water and placedin a 25% solution of sodium hydroxid. heated to about 160 F. until theenamel has been dissolved, which may be ten or fifteen minutes. Thearticle is then washed and dried. In case the enamel is very heavy orconsists of more than one coating. the removal may not have beencomplete, in which case the same procedure is followed asecond or third-third treatments.

Patented July 16, 1918.

Application filed September 5, 1917. Serial No. 189,735.

time or until the removal is complete. Two to five minutes treatment inthe acid have been found to be best for these second and Instead ofhydrochloric acid other mineral acids may be employed. and in likemanner other alkaline baths may be substituted for the sodium hydroxid.The strengths of the solutions may also be varied. and the baths may beeither hot or cold.

I am aware that patents have been granted to Gustav Spitz. Nos.1.055.678 and 1.065.101. on March 11. 1913 and June '21. 1913.respectively. and to George \V. Goetz. No. 528.156. on moval of vitreousenamels. but these processes depend entirely on the use of caustic orother alkali at relatively high temperatures. whereas my invention makesuse of alkali only in a secondary way, the enamel first being softenedand rendered porous by the acid. My process is, therefore. fundamentallynew and does not make use of the principles involved in the above citedpatents. It-is also more economical. since the amount of alkali consumedis small. and the process can be carried on rapidly on a large scalewith the use of comparatively little heat. power or labor.

'hat I claim as new is:

1. The herein described process for removing vitreous enamel from ametallicbase which comprises rendering the enamel porous by treating thearticle with an acid solution and then loosening the enamel by analkaline solution.

2. The herein described process for removing vitreous enamel from ametallic base which comprises first treating the articles with ahydrochloric acid solution of about 10% strength heated to about 160.and then with a sodium hydroxid solution of about 25% strength heated toabout 160.

RAYMOND D. COOKE.

October 30. 1891. for the re-

